We’ve seen some wet weather lately as typical La Nina conditions affect most of the country.  But what lies ahead for the rest of Autumn?  As I’ve said before I’m not a huge fan of long range forecasts but you can take a decent punt using current weather patterns.

February saw 3 significant rain events…now heading into March it’s clear the patterns have again changed.  Perhaps into a more Autumnal pattern with changeable conditions and cooler evenings.

But I wonder just how warm Autumn will be – especially the next month or so.  Some of us were shocked into a taste of winter last week as that polar blast moved up the country.  The poor old east and southern coastlines of the South Island have had a bad run of cold weather over the past 4 to 6 weeks after such an incredible January. 

I’m predicting we’ll see cooler conditions in the west and drier conditions in the east – with the wettest weather in the southern half of the South Island.

The biggest difference from our Summer this year to the one last year was the fact that our highs weren’t centred over us.  Last summer they anchored firmly over us blocking rain and cold winds.  This year they are mainly anchored near Tasmania and only when they strengthen do they spread a ridge over us.  When they weaken the high air pressure retreats back into the Tasman Sea allowing cooler winds to spread up the nation.  This hasn’t been the case 100% of the time but certainly we’ve seen a lot of the highs over Tasmania or in the Tasman – and not as many directly over us.

Now this set up means New Zealand lies on the eastern side of the high.  The winds on the eastern side of a high come from the south.  That’s why we’re getting these cooler winds over many western and southern areas.   There’s more of an easterly flow over northern New Zealand at the moment.  If the highs stay far enough south Auckland and Northland may see more south-easterlies.  A dry direction for Auckland but more showery for places like Whangarei.

If the predominant wind is a south westerly for most other places then we can assume those in the east from Christchurch northwards, especially from Hawkes Bay to Gisborne, will see less rain as it mostly falls in the west.  Meanwhile those lows attacking from the south or south east of New Zealand should keep the shower clouds pumping in to Southland and coastal Otago and maybe southern Canterbury.

Just my thoughts.  Of course we still have La Nina with us so we’re still at an increased risk of tropical or sub-tropical lows coming our way.

BLOG by head weather analyst Philip Duncan